The design of hard and superhard materials is motivated by a demand for robust, chemically diverse compounds for industrial applications ranging from abrasives and cutting tools to protective coatings. Although diamond, with the highest known hardness of about 70 GPa to about 100 GPa, has traditionally been used to fulfill many of these applications, there are limitations to its use. For example, diamond is typically not used to cut steel and other ferrous metals because of the detrimental formation of iron carbide during high-speed machining. Therefore, there continues to be a quest for synthetic materials that can be used in place of diamond. Cubic boron nitride (or BN), with the second highest known hardness of about 45 GPa to about 50 GPa, is typically used to cut steel. However, synthesis of cubic BN is often carried out under extreme pressures greater than about 5 GPa and extreme temperatures greater than about 1500° C., rendering cubic BN cost-prohibitive for certain applications. Two other compounds have been synthesized recently, namely B6O and cubic BC2N, which rival the hardness of cubic BN. However, their syntheses also typically involve extreme pressures, exceeding about 5 GPa for B6O and about 18 GPa for BC2N.
It is against this background that a need arose to develop the rhenium boride compounds and related tools, articles, and methods described herein.